1. Field of the Invention
The invention relates to an operating pedal, and particularly to improvement of an operating pedal that includes a joining portion at which two members are overlapped with each other and welded to each other.
2. Description of the Related Art
An operating pedal, in which a boss with a cylindrical shape is disposed to extend through a pedal arm, and integrally welded to the pedal arm, is known. The pedal arm is made of a thin plate and has a hollow structure. The operating pedal is supported to be pivotable around a center line of the boss. A vehicle operating pedal described in Japanese Patent Application Publication No. 2007-122610 (JP-A-2007-122610) is an example of the operating pedal. In the vehicle operating pedal, a pedal arm, which is made of a thin plate and has a hollow structure, is formed by welding outer peripheral portions of paired half bodies to each other. Each of the paired half bodies has a shape obtained by dividing the pedal arm in a vehicle width direction. A boss is disposed to extend through boss attachment cylindrical portions provided in the half bodies by operating a burring-hole forming process. The boss is integrally fixed to the boss attachment cylindrical portions.
FIG. 6A is a sectional view explaining an example of a joining portion at which a pedal arm 14 and a boss 100 are joined to each other in a conventional operating pedal. FIG. 6A is a diagram corresponding to a section taken along a line IIIA-IIIA in FIG. 2. The pedal arm 14 is formed by welding outer peripheral portions of paired half bodies 32 and 34 to each other. Each of the paired half bodies 32 and 34 has a shape obtained by dividing the pedal arm 14 in the vehicle width direction. Thus, the pedal arm 14 is made of a thin plate and has a hollow structure. Outer peripheral flanges 32f and 34f are provided in the half bodies 32 and 34, respectively. While the outer peripheral flanges 32f and 34f are overlapped with each other, the outer peripheral flanges 32f and 34f are integrally welded to each other, for example, by arc welding. A first joining portion W1 (a blacked-out region) is a joining portion at which the outer peripheral flanges 32f and 34f are joined to each other. Boss attachment cylindrical portions 32g and 34g with a cylindrical shape are provided in the half bodies 32 and 34, respectively, by operating a burring-hole forming process and the like. The boss 100 with a cylindrical shape is disposed to extend through the boss attachment cylindrical portions 32g and 34g. The boss 100 is integrally fixed to the boss attachment cylindrical portions 32g and 34g, for example, by arc welding or laser welding. Second joining portions W2 (mesh regions) are joining portions at which the boss attachment cylindrical portions 32g and 34g and the boss 100 are joined to each other. The boss attachment cylindrical portions 32g and 34g and the boss 100 are discontinuously joined to each other at the joining portions located at predetermined intervals around a center line O.
However, when the boss 100 and the boss attachment cylindrical portions 32g and 34g are welded to each other, for example, by plasma arc welding while the boss 100 is fitted in the boss attachment cylindrical portions 32g and 34g, and outer peripheral surfaces of the boss 100 are overlapped with the boss attachment cylindrical portions 32g and 34g, because the thickness (plate thickness) of each of the boss attachment cylindrical portions 32g and 34g is smaller than the thickness of the boss 100, heat input to the boss 100 tends to be insufficient, and heat input to the boss attachment cylindrical portions 32g and 34g tends to be excessive. Thus, joining failure is easily to occur. That is, the amount of heat input to the boss 100 needs to be larger than the amount of heat input to the boss attachment cylindrical portions 32g and 34g, in order to generate a molten pool, and as a result, there is a problem that, for example, a throat of weld is decreased in thickness due to a decrease in the amount of molten metal in the boss attachment cylindrical portions 32g and 34g, and expansion of a melting width (expansion toward a right side in FIG. 6B. FIG. 6B is a sectional view showing an enlarged VIIB portion in FIG. 6A, which is rotated by 90° in a counterclockwise direction. The thickness (throat thickness) D of the joining portion at a position near a border between the second joining portion W2 and the boss attachment cylindrical portion 32g of the half body 32 becomes small, and therefore, there is a possibility that joint strength may be deteriorated. In addition, because the amount of heat input to the boss 100 becomes large, there is a possibility that heat strain may occur in the boss 100, and the inner diameter of the boss 100 may be changed, and thus, performance of supporting the boss 100 using the support shaft may be deteriorated.
The problems occur not only in the joining portion between the pedal arm and the boss, but also in other joining portions, for example, a joining portion between the pedal arm and the pedal sheet.